Various industries utilize chemicals which, when used in a particular application have a tendency to foam. This foaming phenomenon is oftentimes an undesirable by-product associated with the use of these chemicals, and its presence may have detrimental consequences. In an effort to try and combat this foaming phenomenon, various defoamers and antifoam additives have been formulated which either reduce the amount of foam formed or knock-down the foam at a specific point in the process.
Companies which manufacture and market these defoamers and antifoam additives have become aware of the importance of good bench testing for determining the effectiveness of their products. A good bench test is one which most closely simulates the environment or conditions under which these defoaming or antifoaming additives will be employed, i.e., the customer's process or application. In many industries, such as pulp and paper, defoamers are used as production aids in the respective processes. In these types of applications, defoamer or antifoam additives are employed to maximize productivity and insure against quality problems. These additives, though they do contribute to the cost associated with the particular process, are nevertheless less expensive than the cost of waste stemming from a loss in production capacity or inferior quality of the product formed. Due to the importance of these types of additives in specific processes, defoamer and antifoam users are generally reluctant to experiment with different additives in their processes. The possible benefit which may be derived by employing an improved additive oftentimes fails to outweigh the potential cost of problems if the additive proves ineffective. As a result, bench test methods must be used to assess the performance of any new additive prior to it being recommended to a potential user. A good bench test is a crucial component of new product development, quality control, i.e., fitness for use, and product improvement. These bench tests are also a useful marketing tool in trying to convince a potential user to employ an existing additive or an existing user to employ an improved additive. They serve to demonstrate to a customer that a particular additive will perform effectively in their specific process.
A foam testing apparatus is most often used to perform the above-mentioned bench tests. Defoamer and antifoam additive sales personnel usually carry a defoamer test kit which is capable of testing the effectiveness of an additive in the field. These portable test kits are an invaluable sales tool for they enable the prospective user to see the effectiveness of the additive on various types of foamable liquids. One particular type of defoamer test kit is known as a foam cell. With this type of apparatus, a recirculating fluid flows into and out of the foam cell, whereby the agitation of the fluid in the foam cell causes the fluid to foam. The foam cell is provided with a graduated scale for measuring the height of the foam within the cell. Once a sufficient amount of foam is formed in the cell, i.e., a visually acceptable amount, a defoaming or antifoaming additive is then introduced into the cell. Measurements are then taken to determine the effect of the additive on the foam at the point of introduction, and shortly thereafter, by visually measuring the foam height within the cell.
One type of foam testing apparatus known as an annular foam cell that is used in the industry is disclosed in U.S. Pat. No. 3,107,519, comprising a measuring cylinder open at the top and having a discharge at the bottom. A foam cup, shorter and of smaller diameter than the cylinder, is disposed therein. A long slender tube extends at one end into the cup, with its other end being connected to the outlet of a recirculating pump. In operation, a measured quantity of liquid is continuously pumped into the foam cup causing both the liquid and resultant foam which is formed to spill into the cylinder. Once an adequate amount of foam has been formed, a defoaming additive is then deposited into the cylinder. The effectiveness of the defoamer is determined by measuring the initial drop in foam level, and suppression of further foam formation over a predetermined amount of time.
It has been observed that the afore-mentioned foam testing apparatus has certain deficiencies. For example, it is difficult to accommodate a wide variety of process liquids having varying degrees of foaming ability in one apparatus or employing one test method. These types of liquids are referred to in the industry as high foaming and low foaming liquids. According to the above-cited patent, the testing of these types of liquids requires the further use of an aspirator, if necessary, located in the line just above the entrance to the tube to increase foam generation, or throttling the recirculation rate to reduce the rate of foam generation. Increasing the flow rate of low foaming liquids to generate foam helps the evaluation process, but there is a practical limit to the amount of flow the cell can accommodate. A nozzle or aspirator has limited benefit because of the severe restrictions it imposes on the recirculation flow rate. In other situations, the foaming process medium is too foamy for the foam test apparatus of the prior art. Reducing the circulation flow rate makes the system slower to react and diminishes the benefit of an annular foam cell design. Thus, it would be advantageous to have a better means of adapting a foam cell apparatus to optimize foam generation rates for different foaming media enabling comparison thereof.
Other types of foam testing apparatus utilize two separate foam cylinders to measure the effectiveness of defoaming additives on high and low foaming liquids. One cylinder is specifically ! designed to accommodate high foaming liquids, while the other is designed to promote foaming of low foaming liquids. The disadvantages associated with such test kits are obvious. The cost of putting together such a test kit is significantly increased, for now two foam cells have to be employed. Also, the potential for breakage, coupled with the resultant down-time of the testing system, is now doubled.
Therefore, it would be advantageous, and it is a primary object of this invention to provide an apparatus with an improved foam cell wherein a single cell can be employed to test the effectiveness of both high and low foaming liquids.
A related phenomenon known as entrained air has been found to be just as, if not more, detrimental to industrial processes as foaming. Defoamer and antifoam additives are also used to dissipate any entrained air which manifests itself during industrial processes. It has been found that by employing an in-line density sensor in combination with the foam testing apparatus of this invention, it is possible to measure the effectiveness of these additives relative to both foam and entrained air dissipation. The in-line density sensor offers the advantage of being capable of quantifying entrained air in addition to, or in place of visual surface foam measurements. This system allows for relatively easy automation of density data since the density sensor is a microprocessor based instrument.
Therefore, it is yet another object of this invention to provide an improved method and apparatus for measuring the effectiveness of defoamer and antifoam additives on entrained air formed during a particular process.